The present invention relates to revenue-class electricity meters.
Revenue-class electricity meters are types of electricity meters used to measure various electrical parameters for the purpose of charging customers for the use of electricity. The quantities of various parameters of electricity measured by revenue-class electricity meters are used as the basis for financial transactions between electricity suppliers (e.g. utilities) and consumers. Consequently, it is necessary for both the electricity supplier and the consumer/customer to have confidence in the accuracy and the integrity of the measurements performed by the revenue-class electricity meter. To achieve this, the revenue-class electricity meter should provide measurements that are within industry-accepted limits for accuracy over a defined range of operating conditions. In addition, the revenue-class electricity meter should provide adequate protection against unauthorized alteration of the measured quantities.
The first requirement has been typically addressed by international or national standards. Protection against unauthorized alteration has been provided by a combination of national and utility-based standards.
In general, conventional security safeguards for revenue-class electricity meters have been mechanical in nature. Such conventional safeguards have relied on several factors related to the fundamental design characteristics of mechanical and electromechanical meters to prevent tampering. Conventional revenue-class electricity meters have been inherently fixed in their configuration (i.e. non-programmable). Conventional revenue-class electricity meters have been typically made-to-order in terms of their service-types (2-el delta, 2.5-el star, 3-el, and so on), in terms of their factory-set VT and CT ratios, their factory-set pulse output constants, and so on. In general, conventional revenue-class electricity meters have been factory-built for a specific type of installation and were not field-configurable or programmable.
Conventional revenue-class electricity meters did not provide any capability for remote reconfiguration (or re-programming) of their operating characteristics. Not only were the service type, VT and CT ratios, and pulse output constants factory-set, but also important functions such as energy and demand registers (e.g.: kWh, kVArh, peak kW Demand), time-of-use calendar re-configuration, time-of-use register resets, etc., also could not be changed or reconfigured.
A conventional revenue-class electricity meter commonly employed a simple mechanical seal as a safeguard to prevent unauthorized persons from modifying or otherwise tampering with the measurements performed by the meter. Traditional S-base meters (socket-based with a glass or similar cover) used this type of anti-tamper seal. With these conventional meters, a metal ring was used to secure the meter to the meter socket. To complete an installation of this type of meter, a utility metering technician affixed a metal or plastic seal so that the metal ring could not be removed without breaking the seal. When the meter was later read by a meter reader, the seal was normally inspected for possible signs of tampering.
With the advent of microprocessor-based meters in the early 1980's, utilities and industrial customers were able to purchase a single power/energy monitoring instrument that could be field-configured for a wide range of installations and service configurations. With these new types of meters (which were not generally revenue-class meters), it was no longer necessary to specify all of the meter characteristics at the time of ordering. Specifically, it was not necessary to specify the type of network to be monitored (for example 4-wire star, 3-wire-delta, single-phase etc.), or the VT and CT ratios, the demand period, or any of several other characteristics that may be unique to a particular installation. One such electricity meter that is highly reconfigurable is the Model 7700ION power meter manufactured by Power Measurement Ltd. of Saanichton, B.C., Canada.
The high level of programmability offered by microprocessor-based meters presented a problem to utilities and customers with regard to preventing unauthorized alteration of programmable meter configuration or revenue register values. Therefore, in general, programmable microprocessor-based meters have not been used as revenue-class electricity meters.
Accordingly, it is an object of the present invention is to provide a programmable revenue-class electricity meter that provides a level of security against unauthorized access or tampering of revenue-related parameters, while leaving the rest of the functionality of the device configurable.
It is a further objective to provide an electricity meter that is reconfigurable remotely in a very secure manner, while still maintaining seal integrity.
It is still a further objective to provide selective access to meter information.